CAREER: Transport and Stability in Biocatalytic Fuel Cells

Columbia University, New York NY

Investigators

Abstract

The mission of this CAREER program is (1) the creation of electrode structures that enhance the reactivity and stability of enzyme bioelectrocatalysts as implemented in high power-density biofuel cells, and (2) the integration of these and other fuel-cell devices into a broad spectrum of education and outreach to promote concepts of engineering product design and new energy systems in communities, schools, and universities. Biocatalytic fuel cell technology has the potential to provide electrical power in conditions where conventional fuel cell and battery technologies fail. While key characteristics of redox enzymes, including selectivity and room temperature activity can be exploited in, for example, physiologically implantable fuel cells, implementation of current biofuel cells is hindered by low catalytic activity and low stability of biocatalytic electrodes. This program addresses both of these issues. The model system to be studied is an oxygen-reducing electrode comprised of porous carbon coated with a crosslinked electrostatic adduct of laccase, an oxygen-reducing enzyme, and an electron-conducting redox polymer hydrogel. Engineering the porous support and its interface with the mediator/enzyme hydrogel to maximize gel distribution will improve enzyme utilization and increase current density. Support structures with porosities near 95% and fiber diameter of order 1 micron or less, consisting of carbon nanotubes or electrospun carbon nanofibers, will be evaluated for impact on catalytic activity of the enzyme-hydrogel adduct. Gas-diffusion electrodes will be developed which take advantage of high-rate oxygen mass transfer in the gas phase to further increase electrode catalytic activity. The issue of stability will be addressed by encapsulation of the biocatalysts in porous silica or other metal oxide by means of sol-gel, aerogel, and wet gel processing. Through-film electron mediation will be enabled using carbon nanotubes and redox polymer mediators. Successful introduction of fuel cells to the marketplace depends on an available workforce of qualified scientists and engineers, and the acceptance of fuel cells by energy consumers. Moreover, the chemical engineering discipline as a whole is currently undergoing a transition from process-oriented design to design of chemical products, of which fuel cells are an excellent example. This CAREER program addresses these needs through educational activities emphasizing new energy systems and engineering product design. Educational programs will include (a) A community-based, hands-on after school program in Energy Systems for disadvantaged high-school students; (b) An enhanced introductory Chemical Engineering course for first-year engineering students presenting the concepts of product design through reverse-engineering and team-based design projects; (c) An advanced Electrochemical Energy Systems course for graduates and senior undergraduates; (d) Immersive research training for secondary, undergraduate, and graduate students. This program advances the knowledge and understanding of biofuel cell design while promoting training and learning of chemical product engineering in the context of energy systems.